The present invention relates to an exhaust gas assembly for an internal combustion engine.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Internal combustion engines for automobiles are increasingly charged using turbochargers to reduce fuel consumption y. Because the weight of the turbocharger also affects the fuel consumption, is a goal to develop particularly lightweight and compact exhaust gas systems, in particular in view of the steadily decreasing installation space within the engine compartment. Turbochargers are subjected to significant mechanical and more particular very high thermal loads during operation. In order to nevertheless achieve a useful service life, attempts have been made to eliminate in the turbocharger thermally induced stress and to increase the fatigue limit under reverse stress. DE 100 22 052 A1 describes one exemplary solution for decoupling the components carrying exhaust gas and the supporting or external sealing structures. This results in components having low surface temperatures.
Another significant goal is an increase in the power density, in particular of diesel engines. The charging technique used in an internal combustion engine represents here an important feature. Existing systems already employ two turbochargers arranged in stages to generate sufficient charging pressure even at low rpm and simultaneously sufficient torque (DE 198 37 978 B4). A combination of a mechanical compressor and a turbocharger has also been proposed (AutoBild 36/2005, page 16). However, the arrangement of the components is complex and control is difficult. The surface area of the components also increases significantly, which results in strong cooling of the exhaust gas. This is detrimental for the desired low emission values, since a downstream catalytic converter operates optimally only at higher exhaust gas temperatures. On the other hand, high loads generate a lot of heat which is introduced into the engine compartment due to the increased surface area. This can lead to problems with various plastic components and additional assemblies located in the engine compartment.
MTZ, 5/2005, Year 66, Pages 334-344, describes a stepped charger for a six cylinder diesel engine, wherein two series-produced turbochargers are connected to an exhaust gas manifold and augmented by corresponding switching and control members. However, this approach fragments the exhaust gas assembly, which increases the installation complexity due to the screw connections and the surface area and hence also cools the exhaust gases.
It would therefore be desirable and advantageous to provide an improved compact and lightweight charger capable of reducing excessive cooling of the exhaust gas even with two-stage chargers to reduce thermal loss and minimize weight.